1. Field of the Invention
The invention generally relates to a semiconductor process and a method of forming a semiconductor device, and more particularly to a patterning method and a method of forming a memory device.
2. Description of Related Art
A non-volatile memory provides the properties of multiple writing, reading and erasing operations of data, and is able to retain the stored information even when the electrical power is off. As a result, the non-volatile memory is widely used in personal computers and consumer electronic products. As the level of integration of a non-volatile memory is getting higher, the critical dimension (CD) thereof is getting smaller. In order to break through the limitation of the light source resolution in a lithography process, a so-called spacer self-aligned double patterning (SADP) method has been developed to increase the level of integration of the device. However, when word lines of a memory are defined with the current techniques, the line-width of the word lines adjacent to the peripheral area is affected by the peripheral area and therefore unable to be accurately controlled to the target value. Therefore, the critical dimension uniformity (CDU) of the word lines is degraded and the device performance is accordingly reduced.